1. Field of the Invention
The present invention relates to ink jet printheads, and, more particularly, to a heater chip for an ink jet printhead.
2. Description of the Related Art
A printhead in an ink jet printer includes a silicon heater chip 10 (FIG. 1a), also termed a “die,” containing a plurality of heating devices (not shown). Chip 10 has a single via 12. However, it is also possible for a chip to have multiple vias 12, such as chip 14 (FIG. 1b) or chip 16 (FIG. 1c). Other variations are of course possible. Each via 12 supplies ink from the backside of the heater chip to the front side of the chip, which is where the heating devices are located.
It is known for a line of die attach adhesive to be dispensed onto a substrate in order to attach the heater chip to the substrate. Since adjacent ones of vias 12 may carry different colors of ink, the line of die attach adhesive must seal around and between each via 12 in order to prevent the inks from mixing together. A problem is that there are no features on the backside of the chips to control the die attach adhesive flow during placement and cure.
To meet the increasing demands on ink jet print quality, the packaging technology must provide better thermal management, more efficient use of space, and precision alignment of ejector nozzles. For thermal management, the die attach adhesive plays a key role. The bond line must be controlled in every dimension. Both the placement, in relation to the substrate and via, and the thickness of the bond line are important. As it is attempted to incorporate more devices on each chip, more chips on each head, and all in a smaller package, there is less room for making the necessary ink seals.
In one known method, die attach adhesive 18 (FIG. 2a) is dispensed onto a substrate 20, and a chip 22 is brought into contact with adhesive 18. Adhesive 18 is forced to flow laterally as chip 22 is lowered into place in the direction indicated by arrow 24 (FIG. 2b). This lateral flow of adhesive 18 can result in a very wide bond line in the X direction as the height of the bond line in the Z direction is decreased.
What is needed in the art is a heater chip that can be adhered to a substrate such that greater control of the die attach adhesive is maintained.